The long term objectives of this research are to (a) develop an inventory of diffusible ions in various cells and tissues which represent important components involved in critical developmental processes in early chick development, (b) to correlate this information with other known biochemical data, and (c) to interpret these data as they relate to developmental events. The specific aims include: (a) to improve quick-freezing methods for cryosectioning and analytical studies; (b) to survey diffusible ion concentrations in cells, tissues and extra-cellular compartments of the developing chick embryo, and (c) to correlate the ion concentrations in various compartments of the embryo with significant cellular changes and morphogenetic events. Acheivement of these aims will provide important information in the understanding of normal development and in development perturbated by various experimental manipulations, teratogenci agents, or aging. Chick embryos will be quick-frozen by cryogens and cryosectioned by methods which avoid the mobilization of diffusible ions. Sections will be freeze-dried, viewed and subjected to elemental analysis in an analytical electron microscope. Qualitative and quantitative data will be accumulated in various cellular and embryonic compartments, subjected to computer analysis and interpreted in light of known developmental events occurring in time and space.